This invention relates to helicopters and particularly to a warning system that provides sufficient time for the pilot to avoid a tail contact during a landing operation.
Heretofore, the helicopter provided means for warning the pilot of a potential tail contact whenever the wheels are in the down or landing position, the aircraft is below 150' and the nose of the helicopter is above 10.degree. referenced with the horizon. When all of these criteria were met, a sound signal was imposed in the intercom system. Obviously, these criteria were not necessarily indicative of the tail striking and as a matter of fact the criteria could exist for a normal landing approach. Hence, the signal nonetheless was actuated and has been a cause of annoyance to the pilot.
Our invention contemplates providing a warning signal solely when a tail contact is imminent and a normal landing cannot ensue without corrective action. Hence, our invention is designed to scale the altitude and attitude signals such that when they are equal and opposite in voltage and phase the comparator will trip turning on a relay driver which will cause the warning note to be applied to the intercom system. A rate of descent signal is also summed serving to bias the line upward varying in proportion to the rate of descent. Thus sufficient warning prior to tail contact will allow pilot sufficient time to remedy the situation.